Fish Oils: Health Benefits, Facts, Research.

Fish oils come from fatty fish, also known as oily fish, specifically the tissue of fatty fish, such as trout, mackerel, tuna, herring, sardines, and salmon.

Fish oils are of interest to nutritionists and health care professionals because of two main ingredients: DHA (docosahexaenoic acid), and EPA (eicosapentaenoic acid) – both types of Omega-3 fatty acids.

The fillets of oily fish contain up to 30% oil; this figure may vary. Whitefish, on the other hand, only contain high concentrations of oil in the liver, and have much less oil. Apart from omega-3 fatty acids, oily fish are also good sources of vitamins A and D. Whitefish also contain these nutrients, but at much lower concentrations.

Health experts commonly tell people that oily fish have more health benefits than white fish. However, their recommendations have never been compellingly proven scientifically in large population studies.

Many health authorities around the world advise people to consume either plenty of oily fish or to take supplements, because of their supposed health benefits. Studies over the last ten years have produced mixed results regarding the benefits of the dietary intake of fish oils.

Some people confuse fish oils and cod liver oil – they are different. Fish oils are extracted from the tissue of deep seas oily fish such as tuna, mackerel, herring and salmon. Cod liver oil, by contrast, is extracted solely from the livers of cod. Fish oils contain higher amounts of omega-3 fatty acids than cod liver oil, but lower amounts of vitamins A and D.

Possible health benefits of fish oils

Over the last ten years, there have been dozens of studies on fish oils and omega-3 oils. Some have backed up these claims, while others have not.

Fish oils are said to have a number of health benefits if they are included in a human diet, including:

1) Multiple sclerosis (MS)

Fish oils are said to help people with MS. However, a study carried out by researchers from University Hospital in Bergen, Norway, in April 2012 found that omega-3 fatty acids do not help people with MS.

2) Prostate cancer

Fish oils may reduce a man’s risk of developing prostate cancer if they follow a low-fat diet, one study found, while another linked omega-3 levels to a higher risk of aggressive prostate cancer.

A study published in the Journal of the National Cancer Institute found that omega fish oils raise prostate cancer risk. The authors, from the Fred Hutchinson Cancer Research Center, reported that high fish oil intake raises the risk of high-grade prostate cancer by 71% and all prostate cancers by 43%.

3) Post-natal (post-partum) depression

Fish oils consumed during pregnancy may help protect mothers from post-partum depression – Dr. Michelle Price Judge, of the University of Connecticut School of Nursing, said after carrying out a study in 2011 “DHA consumption during pregnancy at levels that are reasonably attained from foods has the potential to decrease symptoms of postpartum depression.”

4) Mental health benefits

A pilot study carried out in 2007 suggested that fish oils may help young people with behavioral problems, especially those with ADHD. The eight-week study demonstrated that children who consumed between 8 and 16 grams per day of EPA and DHA (the long chain omega-3 fatty acids found in fish oil) showed significant improvements in their behavior (rated by both their parents and the psychiatrist working with them).5

5) Memory benefits

Omega-3 fatty acid intake can help improve working memory in healthy young adults, researchers reported in the journal PLOS One (October 2012 issue).

The benefits of fish oils in aiding cognitive function in older populations may be less beneficial, however. A study by researchers at the University of Iowa suggested that high levels of omega-3 are of no benefit to cognitive decline in older women.

6) Heart benefits

Omega-3 fatty acids found in fish oils may protect the heart from mental stress. A study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology revealed that people who took fish oil supplements for over a month experienced less mental stress in measurements of cardiovascular health than those who did not.

We look closely at all of the studies related to fish oils and the heart on the next page.

7) Protection from Alzheimer’s disease

Claims were made for many years that regular fish oil consumption would help prevent people from developing Alzheimer’s disease. However, a major study in 2010 found that fish oils and a placebo were no different in Alzheimer’s prevention.

In contrast, a study published in Neurology in 2007 reported that a diet in fish, omega-3 oils, fruit and veggies reduces dementia and Alzheimer’s risk.

8) Protection from vision loss

Adequate dietary consumption of DHA protects people from age-related vision loss, Canadian researchers reported in the journal Investigative Ophthalmology & Visual Science.

9) Epilepsy

A 2014 study published in the Journal of Neurology, Neurosurgery & Psychiatry claims epilepsy patients could reduce seizure frequency by consuming low doses of omega-3 fish oil every day.

The research team at the University of California-Los Angeles (UCLA) School of Medicine, says their findings may be particularly useful to epilepsy patients who no longer respond to medication

10) Schizophrenia and psychotic disorders

In what was believed to be the first study of its kind, research has revealed the omega-3 fatty acids found in fish oil may be effective in reducing the risk of psychosis.

The study, published in Nature Communications, details how a 12-week intervention with omega-3 supplements substantially reduced the long-term risk of developing psychotic disorders.

11) Benefits for the fetus

Omega-3 consumption may help boost fetal cognitive and motor development. In a study published in 2008, scientists from L’Université Laval found that omega-3 consumption by the mother during her last three months of pregnancy improved her baby’s sensory, cognitive and motor development.

What are Omega-3 fatty acids?

grilled salmon

Omega-3 fatty acids are types of fat commonly found in plant and marine life oils. There are two types which are plentiful in fatty fish:

    • Eicosapentaenoic acid (EPA) is an Omega-3 fatty acid that is found in fatty fish. When we talk about omega-3 fatty acids in fish, we are usually referring to EPA.

      EPA is a precursor to prostaglandin-3, a platelet aggregation inhibitor, thromboxane-2 and leukotriene-5. Fish do not produce EPA, they obtain it from the algae they eat.


  • DHA (docosahexaenoic acid) is an omega-3 fatty acid that is a main component of the human retina (in the eye), sperm, and cerebral cortex (in the brain).

    40% of all the polyunsaturated fatty acids (PUFAs) in the brain consist of DHA. DHA makes up 60% of the PUFAs in the retina. Half of the neuron’s plasma membrane weight is composed of DHA. Breast milk is rich in DHA.

Do fish oil supplements offer heart benefits?

Experts and members of the general public believe that a high consumption of omega-3 oils has heart benefits. However, studies have produced mixed results.

No heart benefits found – a review of 20 different studies published in JAMA (Journal of the American Medical Association), involving almost 70,000 people, surprisingly found no compelling evidence linking fish oil supplements to a lower risk of heart attack, stroke or early death.

Heart benefits found – a 2011 study, on the other hand, carried out by researchers at Michigan Technological University, found that fish oil consumption can improve blood flow by reducing triglyceride levels, as well as slow down the growth rate of atherosclerotic plaques.

Fish oils help patients with stents in their arteries. People with stents in their heart who took two blood-thinning drugs as well as omega-3 fatty acids were found to have a lower risk of heart attacks compared to those not on fish oils.

Are low Japanese heart disease rates linked to high fish oil consumption?

Researchers from the University of Pittsburgh Graduate School of Public Health set out to determine why the incidence of heart disease in Japan is much lower than in the USA, Canada, Western Europe and Australasia.

They reported in the Journal of the American College of Cardiology in April 2008 that omega-3-rich fish consumption in Japan is much higher than in other developed nations. The authors believe that the greater consumption of fish oils in Japan is the main contributor to its relatively lower heart disease rates.

The scientists explained that the difference cannot be explained by genetic factors. Third and fourth generation Japanese-Americans have either the same or higher rates of hardening of the arteries (atherosclerosis) than the rest of the US population. Atherosclerosis is a major risk factor for heart disease.

Study lead author Akira Sekikawa, M.D., Ph.D., said:

“Our study suggests that very high levels of omega-3 fatty acids have strong properties that may help prevent the buildup of cholesterol in the arteries. Increasing fish intake to two times a week for healthy people is currently recommended in the U.S. Our study shows much higher intake of fish observed in the Japanese may have strong anti-atherogenic effect.”

Japanese adult males consume approximately 3.75 ounces (100 grams) of fish each day. Their US counterparts eat fish no more than twice a week.

North American diet deficient in omega-3 oils

Americans and Canadians eat too much meat and not enough fish, researchers from the University of British Columbia reported in the American Journal of Nutrition in 2008.

The authors added that the North American lifestyle means people are not getting adequate amounts of dietary omega-3 fatty acids. They emphasized that pregnant and breastfeeding women particularly need to make sure they consume plenty of omega-3 oils.

They found that North American women’s babies did not do as well on eye tests if they were deficient in omega-3 fatty acids while they were pregnant.

Which foods are rich in omega-3 fatty acids

The following foods are rich in omega-3 fatty acids:

Spinach - rich in omega 3 fatty acids
Spinach is rich in omega-3.
  • Oily fish – anchovies, herring, sardines, salmon, trout, and mackerel.
  • Flax
  • Hempseed
  • Perilla oil
  • Spirulina
  • Walnuts
  • Eggs (especially the ones that have “high in omega-3 written on the shell)
  • Chia seeds
  • Radish seeds sprouted raw
  • Fresh basil
  • Leafy dark green vegetables, such as spinach
  • Dried tarragon

How can vegans make sure their omega-3 fatty acid intake is sufficient?

Without proper planning, vegans and vegetarians have a much higher risk of being omega-3 deficient than humans who eat animal-sourced proteins.

A vegan consumes no animal-sourced protein at all, not even honey while a vegetarian may include eggs and dairy in their diet. The risk of not consuming enough omega-3 fatty acids is higher for vegans than vegetarians if they do not plan their diets well.

According to, vegans may obtain their necessary omega-3 supplies by either taking supplements or adding plant-sourced omega-3 foods to their diet.

Several foods sold in shops and supermarkets have omega oils added to them, such as many kinds of margarine and spreads. See the list of foods with omega oils above and select the plant-based ones.

Flaxseed and rapeseed oils are very high in omega-3 fatty acids while soybean and walnut oils are high in omega-6 fatty acids. However, you should remember not to cook these at a high temperature.